远程调用归纳

HttpClient和HttpURLConnection

远程调用我们首先想到微服务的组件OpenFeign，但是在单体项目中我们不可能去集成一个专门的远程调用服务，可以使用常见的Http API或者使用Springboot自带的RestTemplate

【解决方案】如何使用 Http API 代替 OpenFeign 进行远程服务调用 - CodeBlogMan - 博客园 (cnblogs.com)

java使用httpclient 、HttpURLConnection 发送第三方请求 使用详解、总结。HttpClient 的使用_java doget 设置请求头-CSDN博客
这里附上使用URLConnection进行远程调用的工具类方法

    public static String sendPost(String url, String param) {
        PrintWriter out = null;
        BufferedReader in = null;
        StringBuilder result = new StringBuilder();
        try {
            log.info("sendPost - {}", url);
            URL realUrl = new URL(url);
            URLConnection conn = realUrl.openConnection();
            conn.setRequestProperty("Accept", "application/json");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            conn.setRequestProperty("Accept-Charset", "utf-8");
            conn.setRequestProperty("Content-Type", "application/json");
            conn.setDoOutput(true);
            conn.setDoInput(true);
            out = new PrintWriter(conn.getOutputStream());
            out.print(param);
            out.flush();
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8));
            String line;
            while ((line = in.readLine()) != null) {
                result.append(line);
            }
            log.info("recv - {}", result);
        } catch (ConnectException e) {
            log.error("调用HttpUtils.sendPost ConnectException, url=" + url + ",param=" + param, e);
        } catch (SocketTimeoutException e) {
            log.error("调用HttpUtils.sendPost SocketTimeoutException, url=" + url + ",param=" + param, e);
        } catch (IOException e) {
            log.error("调用HttpUtils.sendPost IOException, url=" + url + ",param=" + param, e);
        } catch (Exception e) {
            log.error("调用HttpsUtil.sendPost Exception, url=" + url + ",param=" + param, e);
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                log.error("调用in.close Exception, url=" + url + ",param=" + param, ex);
            }
        }
        return result.toString();
    }

    public static String sendGet(String url, String param, String contentType)
    {
        StringBuilder result = new StringBuilder();
        BufferedReader in = null;
        try
        {
            String urlNameString = StringUtils.isNotBlank(param) ? url + "?" + param : url;
            log.info("sendGet - {}", urlNameString);
            URL realUrl = new URL(urlNameString);
            URLConnection connection = realUrl.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            connection.connect();
            in = new BufferedReader(new InputStreamReader(connection.getInputStream(), contentType));
            String line;
            while ((line = in.readLine()) != null)
            {
                result.append(line);
            }
            log.info("recv - {}", result);
        }
        catch (ConnectException e)
        {
            log.error("调用HttpUtils.sendGet ConnectException, url=" + url + ",param=" + param, e);
        }
        catch (SocketTimeoutException e)
        {
            log.error("调用HttpUtils.sendGet SocketTimeoutException, url=" + url + ",param=" + param, e);
        }
        catch (IOException e)
        {
            log.error("调用HttpUtils.sendGet IOException, url=" + url + ",param=" + param, e);
        }
        catch (Exception e)
        {
            log.error("调用HttpsUtil.sendGet Exception, url=" + url + ",param=" + param, e);
        }
        finally
        {
            try
            {
                if (in != null)
                {
                    in.close();
                }
            }
            catch (Exception ex)
            {
                log.error("调用in.close Exception, url=" + url + ",param=" + param, ex);
            }
        }
        return result.toString();
    }